The use of inexpensive polymeric packaging containers has become popular, especially with various food products. One example where these containers have been used is in modified atmosphere packaging. One example of a modified atmosphere packaging is case-ready processing which generally refers to a type of packaging that occurs regionally into point of sale units (e.g., a pound of ground beef or other products) These point of sale units are packaged and ready for display to the customer. This is in contrast to conventional supply chains for meat products that typically involve shipment of large cuts of meat (e.g., a side of beef) to the retail grocer who will divide the meat into the point of sale units.
Containers used with case-ready packaging often are sealed by a lidding film and, thus, require the container surface to be sealable with the lidding film. These containers may include a substrate and a film layer(s) attached to the substrate. To improve the gas barrier property of the container, the film layer(s) of these containers often have barrier resin such as ethylene vinyl alcohol copolymer (EVOH), and the associated tie layer resin such as ethylene methyl acrylate copolymer (EMA) and/or ethylene vinyl acetate copolymer (EVA).
One problem with making polymeric packaging involves costs associated with unused scrap material. Scrap material is generated from (a) unusable containers that are not within manufacturing specifications or (b) trim material produced during the formation of the container The scrap material may come from the substrate alone that forms the container or in combination with the film that forms the container. To reduce costs, it is desirable to use or recycle as much scrap material as possible in manufacturing the containers. The amount of recycled material used, however, should not compromise the quality of the container or raise other issues such as the processability of making the container.
For example, containers using scrap material having EVOH can have reprocessing problems such as degradation under high processing temperatures. The degradation can be exacerbated by the fact that EVOH has an affinity for attaching to metal, such as that used in extruders, that can extend the exposure of EVOH at these high temperatures. The degradation of EVOH can result in the appearance of undesirable black specks in the substrate.
Materials such as ethylene methyl acrylate copolymer (EMA) and ethylene vinyl acetate copolymer (EVA) have reprocessing problems such as cross-linking under high processing temperatures Cross-linking makes reprocessing more difficult because it leads to the formation of gels that increases the viscosity. EMA or EVA also has a tendency to adhere to the metallic surfaces, such as those used in extruders. The cross-linking and adherence lead to process instabilities such as surging or poor gauge control. If the amounts of EMA or EVA in the scrap material differ in the processing, this also leads to process instabilities in that the thickness of the substrate may become difficult to maintain because of a fluctuating pressure profile during extrusion. EMA and EVA may also degrade rapidly which can affect the quality and impact toughness. Degradation of EMA and EVA may also result in the appearance of undesirable brown or black specks in the substrate.
Thus, it would be desirable to manufacture a container that reduces or eliminates the above-noted problems with existing containers.